I. Field of the Invention
This invention relates to chimney pipes for directing exhaust from a fireplace and other appliances to the exterior and, in particular, to an improved joint sealing and locking assembly to connect segments of the vent pipe.
II. Description of the Prior Art
Heating appliances have become increasingly popular as homeowners xe2x80x9ccocoonxe2x80x9d and make use of their homes for entertaining. Gas, real wood and pellet stoves and fireplaces all require the venting of combustion gases to the exterior. It is desirable to direct such combustion gases to the exterior without backdraft. Furthermore, such vent pipes can become hot requiring sufficient insulation around building materials.
Multiple wall vent pipes efficiently direct combustion gases through a main central passageway while coaxial passageways created by larger diameter pipes allow not only for the supply of combustion air to the heating appliance but also act as an insulation barrier. However, connection of the pipe sections in some pipe assemblies is cumbersome requiring fasteners and the like. Additionally, the passageways of the vent pipe must be sealingly isolated to prevent the flow of gases from one to the other. The interior pipe passageway must efficiently direct the majority of gases to the exterior.
The present invention overcomes the disadvantages of the prior known vent pipe assemblies by providing a pipe constructed of sections lockingly and sealingly connected to facilitate pipe runs of unrestricted length.
The direct venting pipe includes a double wall system which allows for the flow of exhaust gases created from the combustion of gaseous hydrocarbons such as natural gas, wood products or propane from the appliance. The pipe allows simultaneous flow of oxygenated air from a suitable source to mix with the gaseous hydrocarbons for more efficient combustion. The piping system incorporates tubes formed of galvanized and stainless sheet metal to create a concentric pipe capable of containing such exhaust or oxygenated gases at elevated or lowered temperatures without leakage through the seams of the joined pipe sections. The pipe sections are sealed by the unique application of an O-ring seal mounted to the pipe ends to prevent any leakage and mixing of the gases. The pipe joints are further joined by a locking system incorporated into the exterior wall which joins the pipe sections longitudinally. The locking system also serves as an integral part of the sealing system by ensuring sealing seating of the O-ring seals.
In one preferred embodiment of the invention, the pipe sections are locked together through a bayonet-type connection by passing locking tabs through corresponding slots then rotating to misalign the tabs from the slots preventing longitudinal separation. Unlike prior known bayonet couplings the tabs and slots are unequally spaced such that the pipe sections can only be joined in one orientation. The unequal spacing of the tabs on one end of the pipe section and the identical spacing of the longitudinal slots on the adjacent pipe section, allows the pipe sections to be joined and disconnected in only one orientation. The longitudinal slots communicate with a peripheral slot accepting the locking tabs. This also allows complete 360 degree rotation before the tabs are realigned with the slots. Prior known locking systems will align every 90 or 120 degrees depending upon the number of tabs. The O-ring seal disposed between the pipe sections is preferably made of a graphite material which has a low coefficient of friction to facilitate manipulation of the joined pipe sections. It has been found that such graphite seals can withstand extreme temperatures and still allow for heat expansion movement of the pipe sections.
In order to maintain the proper spacing between the inner and outer walls and thereby maintain the outer passageway, a plurality of standoffs are disposed between the walls. The standoffs are positionally captured and circumferentially spaced to maintain the desired spacing. The standoffs are fabricated from a metal capable of withstanding the temperature extremes associated with the vent pipe.
The present invention further incorporates termination caps for both horizontal and vertical installations. The termination caps maintain separation of the exhaust and oxygenated air during use. Such caps further serve to repel precipitation and objects from entering the pipe system and are attached to the pipe segments utilizing the unique sealing and locking mechanisms of the present invention.
Other objects, features and advantages of the invention will be apparent from the following detailed description taken in connection with the accompanying drawings